What you can do (better) with ORM

Events & News

12 March 2020 ORM standardsYou can download the first drafts of the ORM standards from the Library. Post your comments in the Forum.

9 March 2020 Understand the Relational Model - before learning anything else!Fabian Pascal's website is probably the best site for learning about the many misconceptions of what a "data model" is and what it is not!

23 May 2019 NORMA Tutorial 1 - updated for Visual Studio 2019This new version of Tutorial 1 contains 63 PowerPoint slides that cover the basic functions of NORMA. The Tutorial has been updated using screen shots from NORMA for Visual Studio 2019. Thanks to Terry Halpin.

1 May 2019 NORMA for Visual Studio 2019The ORM Foundation build of NORMA for Visual Studio 2019 includes fixes for many bugs, most of which still exist in other versions of NORMA. If you would like to test the latest release, please send an email to vs2019@ormfoundation.org. Your email should explain your interest in ORM and the problems that the VS2019 version will help you to solve.

Object-role modeling is a formal method for defining requirements and systems.

I first heard about ORM in the early 1990's. Intrigued by the productivity claims, I flew to Seattle to meet Terry Halpin and the team who were developing InfoModeler for Paul Allen. I was so impressed that I agreed to promote and distribute InfoModeler in Europe.

Years later, after I had taught many business analysts, software developers and university staff how to design databases, Terry asked me to co-author a book about Microsoft's ORM tool "Visio for Enterprise Architects" (VEA). The book was published in 2003.

The first ORM Workshop (1994) was run by Terry Halpin and Robert Meersman on Magnetic Island, Australia. Between 2005 and 2013, the ORM Workshop ran in conjunction with Robert Meersman' s On The Move conference. In 2005, those present agreed by unanimous vote that an ORM Foundation was needed to promote ORM. So I set up this website as a service to the global ORM Community.

ORM 2014 Workshop:was held in the beautiful town of Bolzano, Italy. The two day event started on Monday September 22 at the KRDB Research Centre in the Faculty of Computer Science at the Free University of Bozen-Bolzano. The workshop was hosted by Professor Enrico Franconi and chaired by Professor Terry Halpin. The workshop was followed by a meeting of the Fact Based Modeling Working Group chaired by Serge Valera of the European Space Agency.

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Why ORM?

Software projects often exceed budget and timescale estimates or are cancelled at great cost. People who write about failed IT projects such as journalist Tony Collinsoften cite "vague requirements" as a main cause of project failure.

There would be fewer failed projects if each project started with a clear and agreed set of requirements that defined "what" the project had to deliver before investing in an implementation project.

In 1975, Fred Brooks said"Because our ideas are faulty, we have bugs." (The Mythical Man Month). Twenty five years later, Tony Collins suggested that every project should be split into two separate and independent contracts:The first contractshould define requirements and the second contract should develop the software that conforms to the requirements.

But projects still keep failing which suggests that the "requirements lesson" learned in the 1950's seems to have been dismissed,disparaged or discarded. So let's consider three possible problem sources: sponsoring managers, documentation and development methods.

Somesponsorsdon't have time to get involved in the development process. Others, having agreed a project's benefits and budget, just want the developers to "get on with it". But whatever the style of management, busy sponsors would benefit by ensuring that their needs are understood by developers. So what's most efficient way to do it?

Developers need a clear understanding of what the sponsors want. But requirements documents often contain hundreds of pages of verbose and ambiguous prose. Can this problem be solved?

Over the last 70 years, several methodshave been used to bridge the requirements gap between sponsors and developers.

In the 1950's, the waterfall method was used for the SAGE project. Waterfall was also used by NASA's Apollo project which used IMS, IBM's hierarchical database management system. A hierarchical database is very fast when you want to find data by navigating the hierarchical pointer structure that was specified by the database designer. But it is much harder to extract data that is spread across several branches of the hierarchy.

In 1969, Edgar Codd proposed the relational model as a solution to this problem. The first sentence of his 1970 paper says "Future users of large data banks must be protected from having to know how the data is organized in the machine". Codd introduced the concept of normal form and the related process of normalization which is used to avoid logical inconsistencies, data duplication and excessive maintenance costs.

In 1976, Peter Chen proposed the Entity-Relationship(ER) model for database design. ER remains popular but there is no standard. One problem with ER is that to remove anomalies and redundancies, you must use complex, time-consuming and error prone manual methods such as functional dependency analysis to normalize your ER model. So my "elephant in the room" question for ER modelers is: "If it is so difficult to get rid of the anomalies and redundancies in your ER model, why did you put them there in the first place?" I wonder if Edsger Dijkstra was thinking about ER when he said "All unmastered complexity is of our own making!"

In the 1990's, Grady Booch, Ivar Jacobson andJames Rumbaugh developed UML, a method for designing object-oriented programs. With UML, you define a data structure by using a class diagram. UML is complex, ambiguous and inconsistent which makes it hard to design a class structure that does not contain similar anomalies to those in an ER model.

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Why ORM? ORM is a formal language that can be used to specify requirements, design databases and audit organisations. When you design an object-role model, you avoid the need to write long documents in ambiguous prose. Non-technical sponsors can easily validate an object-role model because it can be expressed in easy-to-understand formal sentences. After the domain experts have validated the object-role model it can be used to generate a fully normalized database schema.

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How do you make an object-role model? An ORM analyst guides sponsors to express their ideas using simple formal sentences such as "The person called Fred was born on 15th July1985." and "The person called Mary was born on 10th July 1990". In ORM we call such formal sentences "facts". The analyst then looks for patterns in the facts. So, for example, these two facts fit the pattern "Person was born on BirthDate". In ORM, we call such patterns "fact types".

Usually, the scope of the fact types must be restricted. For example in the year 2019, you can't have someone with a birth date that is in the year 2020 or later. So you use ORM to put a constraint on the allowable values of "Birth Date". For example: "The value of Birth Date cannot be greater than today's date."

The analyst creates the object-role model by adding new fact types and constraints one at a time. The analyst uses an ORM tool to generate easy-to-read sentences that define the fact types and constraints that have been defined within the object-role model.

This makes it easy for sponsors to check that the model accurately represents their ideas.The sponsor just agrees or disagrees with the formal output generated by the ORM tool.The cycle of input and validation continues until the model is considered complete.

The analyst then generates a data structure against which developers can write application software. The data structure can be a class model or a relational database schema.When generating a relational schema, the ORM tool automatically generates a fully normalized schema which avoids the considerable effort required for manual normalization that is needed in the ER method.

Cost conscious managers should note that ORM helps to reduce development costs and helps to minimize the risk of making costly design errors.

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What is the history of ORM? ORM evolved from European research into semantic modeling during the 1970's. There were many contributors and this paragraph only mentions a few. In 1973, the IBM Systems Journal published a paper by Michael Senko about "Data Structuring".In 1974 Jean-Raymond Abrial contributed an article about "DataSemantics" and in June 1975, Eckhard Falkenberg published his doctoral thesis. In 1976, Falkenberg used the term "object-role model" in one of his papers. Later, Sjir Nijssen introduced the "circle-box"notation together with an early version of the conceptual schema design procedure. Robert Meersman added subtyping, and a conceptual query language.

In 1989, Terry Halpin formalized ORM in his PhD thesis. In the same year, Terry and Sjir Nijssen co-authored the book "Conceptual Schema and Relational Database Design".

ORM Tools:Early ORM tools such as IAST and RIDL* (Control Data) were followed by InfoDesigner(ServerWare), InfoModeler (Asymetrix) and VisioModeler (Visio Corporation). In 2000, Microsoft bought the Visio Corporation and improved VisioModeler. In 2003, Microsoft published its first ORMimplementation as a component of Visual Studio for Enterprise Architects called "Microsoft Visio for Enterprise Architects" (VEA).

Microsoft retained VEA in the high-end version of Visual Studio 2005 but then discontinued its ORM project. The book "Database Modeling with Microsoft Visio for Enterprise Architects" (see sidebar) contains a comprehensive guide to VEA

Terry Halpin led the team that developed the ORM tool called "Natural ORM Architect for Visual Studio" (NORMA). You can download NORMA from the Library.

How can I learn more? The definitive book on ORM is "Information Modeling and Relational Databases -Second Edition". You can order the book by clicking on the image in the sidebar.

The research page describes the scientific experiment that I used to support my MSc dissertation in 2008. I designed the experiment to test the hypothesis that "ORM based methods require at least 25% less effort than alternative methods such as UML and ER."

The Forum contains over 3,000 posts of ORM related discussions. The Library contains ORM software, ORM tutorials and over one hundred ORM presentations of peer reviewed scientific papers given by ORM researchers at ORM Workshops.

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